1. Field of the Invention
The present invention relates to a device for detachably securing a filtering sheet to an air bed using fine solid particles. In such an air bed, the sheet serves to prevent the particles from spreading out of the bed, while the air can pass through the filtering sheet.
2. Description of the Related Art
The air bed of the kind mentioned above has been known and is disclosed in Japanese Patent Publication No. 54-128196 and Japanese Utility Model No. 58-108832. The bed comprises a bed body, a large number of ceramic beads arranged in the bed body, a filtering sheet provided to cover an opening of the bed body, and means for supplying an air stream from a bottom plate of the bed body. The air stream serves to move or agitate the ceramic particles. Due to the movement of the particles and the air stream passed through the filtering sheet, a patient lying on the sheet is floated to some extent. Therefore, the pressure applied to the patient is made uniform, so that the pain of the patient can be mitigated to a large extent and the curing effect can be promoted. Due to the above mentioned merits, air beds have been utilized in hospitals mainly for burnt patients and very sick patients. The sheet of the air bed is made from strong synthetic fibers and is placed on the mass of the solid particles in a slightly loose manner, but the periphery of the filtering sheet is fixed to a flange of the bed in an air tight manner in order to prevent the particles from being spread out of the bed.
Patients do not lay directly on the filtering sheet, but usual bed sheets belonging to respective patients are placed on the filtering sheet. However, the filtering sheet might be stained and soiled. Further, old sheets do not perform the filtering function sufficiently, so that the old filtering sheet has to be replaced by a new one. Therefore, the filtering sheet is detachably secured to the air bed.
In Japanese Patent Publication No. 54-128196, there is disclosed a device for detachably securing the filtering sheet to the air bed. However, this known device utilizes a joint having a special construction, so that the operation for removing or securing the filtering sheet from or to the air bed is rather cumbersome. Further, it is difficult to attain the complete air tight coupling required between the filtering sheet and the bed.